net/netfilter/nf_conntrack_broadcast.c

   1 /*
   2  *      broadcast connection tracking helper
   3  *
   4  *      (c) 2005 Patrick McHardy <kaber@trash.net>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/ip.h>
  14 #include <net/route.h>
  15 #include <linux/inetdevice.h>
  16 #include <linux/skbuff.h>
  17
  18 #include <net/netfilter/nf_conntrack.h>
  19 #include <net/netfilter/nf_conntrack_helper.h>
  20 #include <net/netfilter/nf_conntrack_expect.h>
  21
  22 int nf_conntrack_broadcast_help(struct sk_buff *skb,
  23                                 unsigned int protoff,
  24                                 struct nf_conn *ct,
  25                                 enum ip_conntrack_info ctinfo,
  26                                 unsigned int timeout)
  27 {
  28         struct nf_conntrack_expect *exp;
  29         struct iphdr *iph = ip_hdr(skb);
  30         struct rtable *rt = skb_rtable(skb);
  31         struct in_device *in_dev;
  32         struct nf_conn_help *help = nfct_help(ct);
  33         __be32 mask = 0;
  34
  35         /* we're only interested in locally generated packets */
  36         if (skb->sk == NULL)
  37                 goto out;
  38         if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  39                 goto out;
  40         if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  41                 goto out;
  42
  43         rcu_read_lock();
  44         in_dev = __in_dev_get_rcu(rt->dst.dev);
  45         if (in_dev != NULL) {
  46                 for_primary_ifa(in_dev) {
  47                         if (ifa->ifa_broadcast == iph->daddr) {
  48                                 mask = ifa->ifa_mask;
  49                                 break;
  50                         }
  51                 } endfor_ifa(in_dev);
  52         }
  53         rcu_read_unlock();
  54
  55         if (mask == 0)
  56                 goto out;
  57
  58         exp = nf_ct_expect_alloc(ct);
  59         if (exp == NULL)
  60                 goto out;
  61
  62         exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  63         exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
  64
  65         exp->mask.src.u3.ip       = mask;
  66         exp->mask.src.u.udp.port  = htons(0xFFFF);
  67
  68         exp->expectfn             = NULL;
  69         exp->flags                = NF_CT_EXPECT_PERMANENT;
  70         exp->class                = NF_CT_EXPECT_CLASS_DEFAULT;
  71         exp->helper               = NULL;
  72
  73         nf_ct_expect_related(exp);
  74         nf_ct_expect_put(exp);
  75
  76         nf_ct_refresh(ct, skb, timeout * HZ);
  77 out:
  78         return NF_ACCEPT;
  79 }
  80 EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
  81
  82 MODULE_LICENSE("GPL");